Rotary furnace door design

ABSTRACT

A refractory-free furnace door comprising a plurality of vertically disposed tubular metallic pieces pivotally suspended within a frame member in a side-by-side abutting relationship. The ends of each tubular piece are open so that air will circulate therethrough to air-cool the door.

nited States Patent Hadberg 1 Dec. 12, 1972 ROTARY FURNACE DOOR DESIGN Inventor: Edward J. Hadberg, Gary, Ind.

Assignee: United States Steel Corporation Filed: Jan. 25, 1971 Appl. No.: 109,351

US. Cl. ..266/24, 110/173 R, 110/180 Int. Cl ..F27b 17/00 Field of Search ..266/24; 110/173 R, 180

References Cited UNITED STATES PATENTS Jones ..1lO/l80 Polad ..1 10/180 2,254,900 9/1941 Lessman ..1 10/173 R 3,368,545 2/1968 lbbitson ..1 10/180 FOREIGN PATENTS OR APPLICATIONS 199,198 3/1907 Germany ..1 10/180 Primary Examiner-Gerald A. Dost Attorney-Forest C. Sexton [5 7 ABSTRACT A refractory-free furnace door comprising a plurality of vertically disposed tubular metallic pieces pivotally suspended within a frame member in a side-by-side abutting relationship. The ends of each tubular piece are open so that air will circulate therethrough to aircool the door.

1 Claim, 5 Drawing Figures PATENTED DEC 12 I972 sum 1 OF 2 EDWARD J. HADBERG y ROTARY FURNACE DOOR DESIGN BACKGROUND OF THE INVENTION A rotary-hearth furnace is one having an annular or circular chamber wherein the hearth floor rotates slowly about its vertical axis. Such furnaces are most commonly used in the manufacture of seamless steel pipe, wherein the steel billets or rounds are preheated prior to piercing and forming. In such an operation, the steel rounds are placed, one after another, radially on the rotating hearth floor. The rounds are then suitably preheated as they rotate horizontally through nearly 360 before they are withdrawn.

In most commercial operations, automatic charging machines are used with the rotary-hearth furnaces, whereby the furnace is completely charged and discharged automatically. The steel rounds are conveyed to charging tongs which individually insert .each round after the charging door on the furnace is automatically opened. The charging tongs are then withdrawn as the door closes automatically. The operation is repeated after the hearth floor has rotated sufficiently to receive another steel round. Adjacent thereto, a similar mechanism opens another door as tongs automatically enter and withdraw the steel rounds after completing nearly one revolution.

As on most furnaces, the charging and discharging doors on a rotary-hearth furnace comprise a steel frame and steel outer face with several inches of refractory material packed within the frame against the face. Although such doors are quite suitable on some furnaces, the life span of such doors on rotary furnaces is usually quite short (two months being typical) due to the repeated shock to which the doors are subjected. Specifically, the doors are raised and dropped repeatedly at intervals of about l seconds, so that in a short time, the refractory lining therein' becomes cracked, loosened and falls free. Although the doors can be, and often are, used even after the refractory lining is lost, there is considerable heat loss through the single thin steel face plate. More significantly, however, without the refractory lining, the steel door soon becomes warped or otherwise distorted by the heat, so that it will not function properly. Hence, early door replacement is imperative.

In addition to the above factors which work to shorten the life of rotary-hearth furnace doors, such doors are on occasion completely destroyed by a malfunction of the automatic charging or discharging mechanisms. That is to say, there are occasions when a charging door will fail to open when it is supposed to and, as a result, the charging tongs are literally driven therethrough, demolishing the door and often damaging the charging mechanism and/or the furnace itself.

SUMMARY OF THE INVENTION An object of this invention is to provide a new and improved furnace door, particularly suitable for use on rotary-hearth furnaces, which will have a substantially greater life span than conventional prior art refractory lined furnace doors.

Another object of this invention is to provide a furnace door which can better withstand the repeated shock of being raised and dropped at regular intervals.

A further object of this invention is to provide an all metal, refractory-free furnace door which will resist warpage and deformation upon heating.

Still another object of this invention is to provide a furnace door to be used in combination with automatic charging mechanisms which will minimize damage to itself, the charging mechanism and the furnace in the event the door should fail to open when the charging mechanism is activated.

These and other objects and advantages are fulfilled by this invention, as will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of my invention showing the outer door surface;

FIG. 2A is a horizontal section through the door shown in FIG. 1 at line 22 without the pivotal tubular pieces in place;

FIG. 2B is identical to FIG. 2A except that the pivotal tubular pieces are shown in place;

FIG. 3 is a vertical section through the door shown in FIG. I at line 3-3; and

FIG. 4 is a side elevation of one of the tubular pieces.

DESCRIPTION OF THE PREFERRED EMBODI- MENT Stated simply, the essential feature of my inventive door is the provision of a refractory-free, hollow, reinforced, double-walled door structure through which air will circulate to provide sufficient cooling to prevent warpage or other heat-caused deformation. Such a structure is most simply formed by providing a plurality of closely packed, parallel tubular members, the walls thereof oriented to block the furnace opening.

With reference to the drawings, one preferred embodiment of this invention comprises an open rectangular frame member 10, having a plurality of vertically oriented tubular pieces 12 tightly spaced across the opening through the frame 10. The side walls of tubular pieces 12 provide a substantially solid barrier to the furnace atmosphere, while at the same time, both ends of each tubular piece 12 are open to permit air circulation therethrough.

More specifically, the embodiment shown in the drawing is fabricated almost entirely from rectangular tubing. Because of the softening temperatures to which the door is subjected, I have preferred to use AISI Type 300 Series stainless steel rectangular tubing, with outside dimensions of 4 inches by 3 inches. Although the frame 10 could readily be made from other structural shapes, I have found it convenient to use the single tubing form to minimize variations in material. In addition, the frame, when fabricated with open tubular pieces, will exhibit some degree of self-cooling due to air circulation therethrough as do pieces 12. As shown, frame 10 is fabricated by welding together twelve pieces of the rectangular tubing, three pieces to a side. The opening in frame 10 should preferably be no larger than the opening in the furnace wall the door will cover.

Each vertical side portion of frame 10 is provided with a lateral hole therethrough near the upper end thereof to removably receive a cylindrical pin 14. In addition, each vertical side portion of frame 10 may also be provided with a wedging flange l6 midway along the forward edge thereof. Such wedging flanges 16 are common in prior art furnace doors, and merely serve to hold the door tightly against the furnace opening when the door is in the closed position. That is, the sides of the furnace are then provided with small horizontal rollers (not shown) which are spaced in front of each vertical side portion of the door. Hence, when the door is lowered into the closed position, the wedging flanges l6 engage the inside of the rollers and force the door tightly against the furnace walls surrounding the opening. The tubular pieces 12 are each' provided with lateral holes through the upper end thereof, and then pivotally suspended, within the frame opening, by cylindrical pin 14. As shown in FIGS. 3 and 4, the lower forward edge and the upper rearward edge of each tubular piece 12 is cut back and rounded so that the lower end of pieces 12 are free to be pivoted into the furnace, about pin 14. In addition, the cut-away edges will serve to better expose the inside of the tubular pieces 12 to the surrounding atmosphere, thereby facilitating air circulation therethrough.

In operation, the door is freely suspended over the furnace opening by cable 18. The door is then automatically opened and closed by an actuating means (not shown) which raises and lowers cable 18. Since the door is fabricated entirely of metal, there is no refractory material therein to be cracked, loosened and lost as the door is repeatedly subjected to the shock of into the door, tubular pieces 12 would merely be pivoted inward, about pin 14, without damage to the door, furnace or charging tongs.

In view of the above detailed description, it should be apparent that other embodiments or modifications could be employed without departing from the spirit of the invention. For example, if charging malfunctions are never encountered, it would not be necessary to pivotally mount the tubular pieces 12, and hence, a simpler frame 10 could be employed. In fact, the frame member 10 could be completely eliminated if so desired. That is, the furnace door could simply comprise a plurality of metallic tubular pieces joined by welding for example, in a side-by-side abutting relationship without a frame portion. Although the use of tubular pieces is perhaps the simplest method of forming such a door, it is also obvious that other materials could be used. For example, the door could be formed by a pair of steel plates forming the inside and outside wall portions of the door and spaced apart by a plurality of reinforcing members so arranged as to provide substantially vertical channels between the plates through which the air will circulate. Other structural forms could obviously be devised.

I claim:

1. A refractory-free furnace door comprising a metallic frame member and a plurality of metallic tubular pieces pivotally suspended in a side-by-side vertical abutting arrangement, so that said tubular pieces can be pivoted inward without damage to said door, the interior portion of said tubular pieces being sufficiently open to the atmosphere at the top and bottom to pro- 

1. A refractory-free furnace door comprising a metallic frame member and a plurality of metallic tubular pieces pivotally suspended in a side-by-side vertical abutting arrangement, so that said tubular pieces can be pivoted inward without damage to said door, the interior portion of said tubular pieces being sufficiently open to the atmosphere at the top and bottom to provide air circulation therethrough to air-cool said furnace door. 